1. Field of the Invention
The invention relates to an image forming apparatus that is suitable for copying, printing, facsimile reproduction, and similar applications.
2. Description of Related Art
Conventionally, an image forming apparatus which is designed to form an image on a recording medium, by modulating particle flows of a toner through a plurality of apertures formed through a particle flow modulator, is known. The particle flows through the apertures are modulated by applying controlled electric potentials, that is an imaging potential and a non-imaging potential, to respective electrodes provided on the particle flow modulator according to image signals.
Described in detail, the particle flow modulator includes an insulating layer, a reference electrode formed on one of the surfaces of the insulating layer, and a segmented conductive layer formed on the other surface of the insulating layer. The segmented conductive layer consists of a plurality of control electrodes. The particle flow modulator has at least one row of apertures formed through the insulating layer and the continuous and segmented conductive layers, such that the apertures correspond to the respective control electrodes. The apparatus also includes voltage applying means for applying selected electric potentials between the reference electrode and each of the control electrodes; toner supply means for providing electrostatically charged toner particles so that flows of the charged toner particles through the individual apertures of the particle flow modulator are modulated by the applied electric potentials; and back electrode means, for positioning the recording medium in the path of the flows of the toner particles, which is provided on an opposite side of the particle flow modulator than the toner supply means. An example of such an image forming apparatus is disclosed in detail in U.S. Pat. No. 3,689,935.
However, in the conventional image forming apparatus thus structured, the amount of toner particles which pass through an aperture A, corresponding to one control electrode to which the imaging potential is applied, differs when an imaging potential is applied to the control electrode corresponding to an aperture B, adjacent to the aperture A, and when the applied potential to aperture B is a non-imaging potential. That is, when an imaging potential is applied to the control electrode of an aperture, the toner particles supplied to the areas surrounding the aperture are moved in the direction of the aperture by the electric field formed by the applied potential and the density of the toner particles in the surrounding areas becomes thin. Therefore, when the imaging potential is applied to the control electrode of the aperture B, the amount of toner particles which passes through the aperture A, adjacent to the aperture B, decreases.
On the other hand, when the non-imaging potential is applied to the control electrode of an aperture, the toner particles supplied to the areas surrounding the aperture are moved in the direction of the surrounding areas by the electric field formed by the applied potential and the density of the toner particles in the surrounding areas thickens. Therefore, when the non-imaging potential is applied to the control electrode of the aperture B, the amount of toner particles which passes through the aperture A, adjacent to the aperture B, increases. As a result, the edge portion of the aperture is emphasized and the image recorded on the recording medium becomes uneven.
In addition, in the conventional particle flow modulator, the tracks of the toner particles which fly to the image recording medium after passing through the aperture corresponding to the control electrode to which the imaging potential is applied differ according to the potential applied to the control electrode of the adjoining aperture, that is, whether an imaging potential or a non-imaging potential is applied. This difference is caused by the electric fields generated between the control electrodes adjacent to each other. As a result, the input image data cannot be faithfully recorded on the image recording medium.